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- ResponseMessage is passed in SendMessageToDeviceCallback
- SharingMessageHandler is requried to call done callback when done

Bug: 1016714
Change-Id: I12e5729d39c9a9046ca7e8ffdfae0047a79d1464
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869218
Commit-Queue: Alex Chau <alexchau@chromium.org>
Reviewed-by: Richard Knoll <knollr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708973}